Quantized data-dependent jitter injection using discrete samples

Abstract

Methods, system, and computer programs for compensating for introducing data dependent jitter into a test signal using a testing instrument are disclosed. The method includes generating a test pattern that comprises a plurality of intervals. Each of the intervals includes a number of redundant samples that correspond to a sample in a test source pattern. The test pattern is digitally modified to generate a modified test pattern that includes data dependent jitter.

1. A method, comprising:
 generating a test pattern that comprises a plurality of intervals, each of the intervals comprising a number of redundant samples corresponding to a sample in a test source pattern, wherein the number of redundant samples is based on a difference between an operating frequency of a tester and an operating frequency of a device under test, the operating frequency of the tester being greater than the operating frequency of the device under test; and 
 digitally modifying the test pattern to generate a modified test pattern that includes data dependent jitter. 
 
     
     
       2. The method of  claim 1 , further comprising applying the modified test pattern to the device under test at the operating frequency of the tester. 
     
     
       3. The method of  claim 1 , wherein digitally modifying the test pattern comprises replacing one or more samples from a particular interval with a sample from an interval preceding the particular interval. 
     
     
       4. The method of  claim 3 , wherein replacing the one or more samples comprises replacing the first sample in the interval with the last sample from an immediately preceding interval. 
     
     
       5. The method of  claim 1 , wherein digitally modifying the test pattern comprises replacing one or more samples from a particular interval with a sample from an interval subsequent to the particular interval. 
     
     
       6. The method of  claim 5 , wherein replacing the one or more samples comprises replacing the final sample in the interval with the first sample from an immediately subsequent interval. 
     
     
       7. The method of  claim 1 , further comprising:
 determining, based on user input, an amount of data dependent jitter to introduce into the test pattern; and 
 determining whether to modify one or more samples of a particular interval of the test pattern based on the determined amount of data dependent jitter. 
 
     
     
       8. The method of  claim 1 , further comprising:
 receiving a data dependent jitter algorithm; and 
 determining whether to modify one or more samples of a particular interval of the test pattern based on the algorithm. 
 
     
     
       9. The method of  claim 1 , further comprising determining whether to modify one or more samples of a particular interval of the test pattern based on an algorithm stored in a memory included in the tester. 
     
     
       10. The method of  claim 1 , wherein modifying the test pattern comprises:
 applying a software-based algorithm to modify the test pattern; and 
 overwriting the test pattern with the modified test pattern. 
 
     
     
       11. The method of  claim 10 , wherein applying a software-based algorithm to modify the test pattern comprises:
 during a first cycle, applying a software-based algorithm to modify the test pattern; and 
 during a second cycle, applying a software-based algorithm to modify the test pattern, the modifications generated during the first cycle being identical to the modifications generated during the second cycle. 
 
     
     
       12. The method of  claim 1 , wherein modifying the test pattern comprises modifying the test pattern in real time using a circuit included in the tester. 
     
     
       13. The method of  claim 12 , wherein modifying the test pattern comprises further
 during a first cycle, applying a software-based algorithm to modify the test pattern; and 
 during a second cycle, applying a software-based algorithm to modify the test pattern, the modifications generated during the first cycle being identical to the modifications generated during the second cycle. 
 
     
     
       14. The method of  claim 1 , wherein the number of samples is about equal to a ratio of the operating frequency of the tester to the operating frequency of the device under test. 
     
     
       15. A testing system, comprising:
 a tester configured to:
 generate a test pattern that comprises a plurality of intervals, each of the intervals comprising a number of redundant samples corresponding to a sample in a test source pattern, wherein the number of redundant samples is based on a difference between an operating frequency of a tester and an operating frequency of a device under test, the operating frequency of the tester being greater than the operating frequency of the device under test; and 
 digitally modify the test pattern to generate a modified test pattern that includes data dependent jitter. 
 
 
     
     
       16. The testing system of  claim 15 , wherein the tester further comprises an analog front end configured to apply the modified test pattern to the device under test at the operating frequency of the tester. 
     
     
       17. The testing system of  claim 15 , wherein the configurations that cause the tester to digitally modify the test pattern further comprise configurations to replace one or more samples from a particular interval with a sample from an interval preceding the particular interval. 
     
     
       18. The testing system of  claim 17 , wherein the configurations that cause the tester to replace the one or more samples comprise configurations to cause the tester to replace the first sample in the interval with the last sample from an immediately preceding interval. 
     
     
       19. The testing system of  claim 15 , wherein the configurations that cause the tester to digitally modify the test pattern further comprise configurations to replace one or more samples from a particular interval with a sample from an interval subsequent to the particular interval. 
     
     
       20. The testing system of  claim 19 , wherein the configurations that cause the tester to replace the one or more samples comprise configurations to cause the tester to replace the final sample in the interval with the first sample from an immediately subsequent interval. 
     
     
       21. The testing system of  claim 15 , further comprising a memory configured to store an algorithm for determining whether to modify one or more samples of a particular interval of the test pattern.